M998 lift pump replacement and bleeding tips

[Enforced_Leo44]

So, I have all (or well, almost) the pieces to replace my lift pump on my '88 M998 6.2L, I read some general tips in this forum like the grease glob on the push rod to make it stay in place
I still have a couple of questions since it's gonna be my first time every replacing a lift pump in a diesel

1) I see that the mounting plate for the pump has its own gasket, can I make one of those on my own by cutting it out from some gasket paper sheet? like Klinger paper

2) Once the pump is on, do I have to bleed the air that got into the system or it doesn't matter? If the bleeding is necessary, how can I perform it?

Thanks for all the advices that I got in this forum, y'all are amazing

 

[Mogman]

Both the gaskets are the same as an older small block chevy (think 1970 350CI) so you can pick them up at the local parts house.
Some just use gasket maker.
After you grease up the rod, put some on the tip going into the block also.
I put the gasket and plate on and with the small 1/4" screws loose, then I put the two pump screws in a few threads, then tighten the small plate screws, this ensures the holes are aligned for when you install the pump and you do not have to try and tighten the small plate screws with the pump in place.

If it was running before installing the pump remove the shutdown (ign) wire from the IP so it does not try to start, if not it will try and start or start, pulling air into the IP, open the filter drain valve and crank it until a steady stream of fuel runs out after the air bleeds out then close the valve and re=install the IP wire and you should be good to go.

IF you have trouble getting fuel out of the filter drain you can apply a small amount of air pressure to the fuel filler tube but do not pressure the tank up too much, I just take a red rag and wrap it around my air nozzle.

Do not crank the engine for more than 5-10 seconds at a time with plenty of time in between for the starter to cool.

EVERY time you return the run switch to off you must wait at least 90 seconds before switching to the run position or you can fry your glow plugs (this is a practice you should always do)

 

[Enforced_Leo44]

Both the gaskets are the same as an older small block chevy (think 1970 350CI) so you can pick them up at the local parts house.
Some just use gasket maker.
After you grease up the rod, put some on the tip going into the block also.
I put the gasket and plate on and with the small 1/4" screws loose, then I put the two pump screws in a few threads, then tighten the small plate screws, this ensures the holes are aligned for when you install the pump and you do not have to try and tighten the small plate screws with the pump in place.

If it was running before installing the pump remove the shutdown (ign) wire from the IP so it does not try to start, if not it will try and start or start, pulling air into the IP, open the filter drain valve and crank it until a steady stream of fuel runs out after the air bleeds out then close the valve and re=install the IP wire and you should be good to go.

IF you have trouble getting fuel out of the filter drain you can apply a small amount of air pressure to the fuel filler tube but do not pressure the tank up too much, I just take a red rag and wrap it around my air nozzle.

Do not crank the engine for more than 5-10 seconds at a time with plenty of time in between for the starter to cool.

EVERY time you return the run switch to off you must wait at least 90 seconds before switching to the run position or you can fry your glow plugs (this is a practice you should always do)

Thanks for all the heads up, for the glow ups, it's not a problem for me since the previous owner bypassed the smart box and installed a "manual" glow plugs system, activated by a button


Second thing, do you have a picture of the cable i should disconnect on the injection pump?

 

[Mogman]

 

[Enforced_Leo44]

View attachment 899608

Alright, perfect, so the correct procedure would be to:

1) replace the lift pump
2) disconnect that cable on the IP
3) open the drain faucet of the filter
4) crank the engine until a steady flow of fuel comes out, letting the starter motor cool between every cranking
5) plug the IP cable back and should be good to go

 

[Enforced_Leo44]

View attachment 899608

wait, just a doubt out of ignorance, wouldn’t the pump still inject the diesel left in the pump itself since it’s mechanically driven?

 

[Mogman]

wait, just a doubt out of ignorance, wouldn’t the pump still inject the diesel left in the pump itself since it’s mechanically driven?
[/QUOTE
It will not try and pump any fuel into the injection lines because it is in shutdown, (otherwise the engine could never be shut down) there is a small rotary pump in the input to the IP which is rather week and hopefully cannot overcome the check valve in the return fitting on top of the pump, removing the wire gives you the best chance of not getting air into the injection lines

 

[Enforced_Leo44]

Aaaah right, I see, the functioning of the IP are still beyond my mechanical comprehension lol, but I'll get there eventually, thanks for the advices!

 

[TNDRIVER]

Aaaah right, I see, the functioning of the IP are still beyond my mechanical comprehension lol, but I'll get there eventually, thanks for the advices!

After reading through this I think a small step has been omitted. I'm sure I'll be corrected if I'm wrong! You need to get the pump "push rod" in a fully retracted position, maybe you saw that in your read through of the info available here? A wrench on the back of the crank balancer can rotate the engine while you can "feel" the end of the push rod to make sure it is as fully retracted as possible, makes this job a lot easier. Just my 2 cents.

 

[Enforced_Leo44]

After reading through this I think a small step has been omitted. I'm sure I'll be corrected if I'm wrong! You need to get the pump "push rod" in a fully retracted position, maybe you saw that in your read through of the info available here? A wrench on the back of the crank balancer can rotate the engine while you can "feel" the end of the push rod to make sure it is as fully retracted as possible, makes this job a lot easier. Just my 2 cents.

Didn’t think about this, I guess that not doing this will make the job harder because I’ll have to fight against the spring of the pump lever to sit it correctly, if the push rod is extended out

 

[87cr250r]

The bolts will draw the pump in against the spring. The problem is that you won't be able to get the pump arm under the pushrod if the rod slides down which it does by gravity.

 

[TNDRIVER]

Didn’t think about this, I guess that not doing this will make the job harder because I’ll have to fight against the spring of the pump lever to sit it correctly,

The bolts will draw the pump in against the spring. The problem is that you won't be able to get the pump arm under the pushrod if the rod slides down which it does by gravity.

if the push rod is extended out

The "grease" they are talking about is to hold the push rod in place while the pump is installed. I personally leave the plate on the block if there is no oil leakage and use a strip of flexible plastic to allow the pump arm to slide under the push rod . Works for me. The grease method works pretty good though.

 

[Enforced_Leo44]

The "grease" they are talking about is to hold the push rod in place while the pump is installed. I personally leave the plate on the block if there is no oil leakage and use a strip of flexible plastic to allow the pump arm to slide under the push rod . Works for me. The grease method works pretty good though.

I'm gonna do a first attempt (hopefully the last as well lol) tomorrow morning, I cut my gaskets from a sheet of gasket paper (Klinger I think is the maker name), gonna grab myself a bit of patience and hope for the best, thanks a lot for all the advices

 

[Enforced_Leo44]

Just the last doubt before the job, wouldn't opening the drain valve of the filter just drain out all of the fuel in it, thus creating a air pocket? Or maybe I'm just missing something about the internals of said filter housing

 

[Mogman]

Nothing really wants to go anywhere, The best way I can describe it is to put you finger over a straw and pull it out of the glass, without something "moving" in the system nothing will come out of the filter.
You of course should open it just before trying to bleed it and immediately close it after cranking the engine.
It is entirely likely you are going to get air in the injection lines, just do not crank it too much and burn up the starter, keep the batteries topped off and if after getting good flow to the filter drain and re-connect the run wire, it may start for a few seconds and die, keep trying conservatively to start it, if that fails then open up the easiest injection lines to get to and try to get some flow there.
It will likely run rough for a short time when it does get going.
I have never had to bust all the lines to bleed the system.

 

[Mogman]

Also of course if you have not, this is a good time to replace the fuel filter..

 

[Enforced_Leo44]

Also of course if you have not, this is a good time to replace the fuel filter..

I took off the filter casing and replaced the filter itself and the separator, is it normal/ok for the new filter to have some play within the casing?

 

[Mogman]

I took off the filter casing and replaced the filter itself and the separator, is it normal/ok for the new filter to have some play within the casing?

Yes.

 

[Enforced_Leo44]

Yes.

Well, in the meantime, I went ahead and got a spin-on filter housing and a truck diesel fuel filter, guess that makes the best solution

 

[Enforced_Leo44]

Yes.

Picked up this thing